The present invention is directed to curable, preferably electron-beam (EB) curable, pressure-sensitive, acrylic-based fumaric interpolymers containing an interpolymerized amount of diesters of unsaturated dicarboxylic acids containing from 2 to 4 carbon atoms, namely, fumaric and maleic acids.
U.S. Pat. No. 2,544,692 to Kuegler et al discloses copolymerization of an acrylic acid with minor amounts of a fumarate diester. Lmulsion and bulk polymerization are stated as being feasible.
U.S. Pat. No. 4,220,744 to Tulacs et al discloses the use of two-stage bulk polymerization to form a viscous liquid containing interoolymerized amounts of dialkyl esters of fumaric or maleic acid.
U.S. Pat. No. 2,642,414 to Bauer et al discloses copolymers of esters of methacrylic acid and a saturated aliphatic monohydric alcohol and a maleinoid ester of a saturated aliphatic monohydric alcohol of from 4 to 14 carbon atoms, and certain organic acids. The maleinoid esters include dibutyl fumarate. The products of the reaction are disclosed to have utility in modifying the pour point of hydrocarbon oils.
The curing of monomers as well as polymers to induce or improve pressure-sensitive properties, is old in the art. Of relevance to the overall concept is U.S. Pat. No. 3,725,115 to Christenson et al, who disclose the preparation of pressure-sensitive adhesives by irradiating a hotmelt composition. The compositions disclosed are coated on release liners and are subjected to electron-beam irradiation of a dosage of from 6 to 8 megarad, leading to high peel strengths. The improved adhesive is then transferred to the face stock.
U.S. Pat. No. 4,069,123 to Skoultchi et al discloses the UV curing of homopolymers of alkyl esters of acrylic and methacrylic acids, and of copolymers of such esters with other comonomers, including C.sub.1 -C.sub.4 alkyl half-esters of maleic and fumaric acids. The polymers are disclosed as being formed by bulk, solvent or emulsion polymerization.
It has not been heretofore known to use diesters of unsaturated dicarboxylic acids such as dibutyl fumarate, in combination with energy curing, to enhance adhesive properties. This is the subject matter of the instant invention.